This invention relates to a coated knit textile fabric for use in an air-holding vehicle occupant restraint system and, more particularly, to a fabric having a plurality of polymeric layers coated thereon for use in such a vehicle occupant restraint system, the method of coating said textile knit fabric, and the air-holding vehicle occupant restraint system formed from such coated fabric.
The current restraint systems for vehicles include driver side air bags which are housed in the steering wheel in a collapsed, folded condition adapted to be deployed instantaneously in an inflated condition by injection of a gas upon the occurrence of a collision. The advent of such driver-side air bags has resulted in a significant decrease in auto fatalities.
Air bag restraint systems have also been located in the dashboard in order to provide a comparable measure of protection to the passenger seated adjacent the driver.
The automotive industry has recently introduced air bags which are housed in the backs of the front seats or in the rear seats to protect the cabin occupants in the event of a collision occurring on either side of the vehicle.
A still further safety feature which is being marketed for passenger vehicles, especially sport utility vehicles (SUV), are air-holding curtains designed to provide a cushioning effect in the event of roll-over accidents. These curtains are housed in the roof of the vehicle and deploy along the interior sidewalls of the SUV""s cabin in the event of a rollover.
One means of improving the efficacy of air-holding vehicle restraint systems has addressed the coatings to be applied to the textile substrate to improve air retention.
In the prior art, coated air bags were made by coating a nylon substrate with chloroprene or silicone. They were not, however, susceptible to heat sealing. In order to ameliorate the problems inherent in chloroprene and silicone rubber coatings, it has been disclosed in the art, for example, Menzel, U.S. Pat. No. 5,110,666, to coat knitted and woven nylon and polyester substrates with polyurethane to provide the desired permeability to better retain the inflation gas.
The use of a polyurethane coated fabric for use in garments and bags is disclosed in Tschirch et al., U.S. Pat. No. 4,284,682 which is assigned to NASA. This patent discloses a process for forming a polyurethane elastomeric film on woven or knitted fabrics made from cotton, rayon, polyester, polyamide, etc. and laminating with pressure and heat. This patent discloses laminating a single layer of polyurethane film on a fabric in order to assure that garments or bags made therefrom would be leakproof.
Despite the advances in air bag coating technology, the problems of controlling air permeability, air pressure, and volume still remain. Another problem resulting in air loss stems from the fact that during the manufacture of the air bags, they are stitched shut by means of sewing. Inherently, each stitch creates a potential leak which adversely affects the integrity and, hence, the air holding capability of the bag, especially when instantaneous deployment of an operative airbag is required.
With the advent of SUV""s, the provision of adequate protection to passengers in the event of multiple rollovers has become of prime importance. One means of obtaining such protection is by providing air curtains which are disposed in a collapsed condition in the header of the SUV and which deploy in the event the vehicle rolls over. The air-holding capability of such air curtains is critical since they must remain inflated for an extended period of time. Unlike air bags which are designed to inflate instantaneously, and also deflate almost instantaneously in order to avoid injury to the driver or the passenger from the bag itself, air curtains used in an SUV, or in a passenger vehicle, must be capable of remaining inflated in the range of about three (3) to about twelve (12) seconds, depending upon the size of the curtain used and the type of vehicle employed. The maximum inflation period should be sufficient to protect the cabin occupants during three (3) rollovers, which are the maximum number of rollovers which are usually experienced.
It has now been found that by coating a plurality of polyurethane layers onto a stretchable fabric substrate, followed by heat-sealing two of such coated substrates together, yields an air-holding restraint system which has superior air-holding characteristics, viz., permeability, as well as volume and pressure retention.